Closure plug improvement

ABSTRACT

An externally threaded closure plug for tightly closing off the internally threaded opening in shipping and storage containers such as drums, pails and the like. The plug is formed as a cup having a bottom wall and threaded cylindrical sidewall terminating in a circumferentially enlarged rim. Immediately beneath the rim of the plug is an annular gasket seat defined by the undersurface of the plug rim, the plug sidewall at the thread root diameter and an annular retaining lip lying in a plane parallel to the undersurface of the plug rim.

BACKGROUND OF THE INVENTION

[0001] This invention is directed to an improved container closure plugand more specifically a threaded plug having a unique gasket retainingfeature.

[0002] In the shipping container industry it is most common tomanufacture drums, pails and the like with one or more dispensing and/orfill openings. Such openings have an internal helical screw thread whichmerges into an unthreaded gasket sealing area. An externally threadedclosure plug carrying an annular sealing gasket is threadedly engagedwithin the opening. Upon tightening the plug, the plug gasket is drawndown tightly against the unthreaded gasket sealing area to provide aneffective sealing of the container. While many millions of drums andother containers have been sealed in this fashion, an occasional problemarises which this invention addresses. That problem has not only to dowith sealing but also with unscrewing of the plug from the containeropening. A critical relationship exists between the plug and its gasketon the one hand and the merger of the container opening thread into theopening gasket seat area on the other. This relationship is such that inpractice upon applying the necessary torque to seal the plug in thecontainer opening, the plug gasket becomes wedged against the run-out ofthe opening internal thread. When the plug is subsequently unscrewed itis an all to common occurrence that this gasket wedging action againstthe opening thread tightly grips the plug gasket. As the unscrewingaction continues a tenuous condition ensues. Most notably as the plugtravels out of the opening the gasket can remain ensnared on theinternal opening thread so that the gasket gets pulled off of its gasketseat position on the plug. Continued rotation of the plug becomesextremely difficult as the gasket jams between the mating threads.Moreover, the gasket itself becomes severely damaged due to thisshredding action which further diminishes the utility of the closure.

[0003] Another negative aspect of this gasket gripping condition is thetendency of the gasket to loop out of its gasket seat during torqueingof the plug. This problem occurs when the plug gasket movement aroundthe unthreaded gasket seat of the opening becomes obstructed causing thegasket to bunch up and form a loop protruding from the edge of theopening. One way for such obstruction to occur is when the plug gasketagain becomes ensnared on the opening thread run-out as the plug now istraveling into the opening. The resultant “looping” condition will mostcertainly create a leakage path and quite likely impart serious damageto the gasket. The commonality between these “gripping” and “looping”problems is, of course, the ability to retain the plug gasket in placeon the plug gasket seat where it belongs and thus prevent it from beingdragged onto the thread interengagement.

[0004] The prior art has recognized the desirability generally ofproviding some positive mechanical retaining means for keeping the pluggasket in place. For example, U.S. Pat. No. 5,211,304 to Stolzmandiscloses a plug construction wherein the gasket is securely retained onthe undersurface of the plug rim with a mechanical interlockingarrangement. This arrangement, however, places the gasket radiallyoutwardly of the plug thread and has no relationship whatsoever to anykind of gasket “gripping” or “looping” problem. Another prior artexample is found in U.S. Pat. No. 2,906,429 to Marchyn which recognizesthe “looping” problems but fails to provide a completely satisfactorysolution. In this patent the plug has a special thread formation wherethe thread borders the gasket seat. Specifically the plug has adiminishing thread that continues around the lower edge of the gasketseat and acts as a partial barrier above the normal plug thread. Thismodified thread configuration, however, falls short of providingadequate protection against the “gripping” phenomenon as will be clearlyseen hereinafter.

BRIEF SUMMARY OF THE INVENTION

[0005] According to the present invention, a closure plug is formed witha cylindrical threaded sidewall, the sidewall terminating in acircumferentially enlarged rim and having an annular gasket seatimmediately under the plug rim in substantial axial alignment with thescrew thread root diameter wherein a circumferential gasket retaininglip is interposed the plug gasket seat and the sidewall thread.

[0006] Also according to the present invention the closure plug iscombined with a threaded container wall opening and has a resilientsealing gasket lying in close proximity to said internal thread wherebysaid gasket retaining lip prevents interengagement with said gasket andsaid opening thread.

[0007] The instant closure of the instant invention presents a longsought after solution to the above mentioned “gripping” and “looping”problems in a simple straightforward manner. The plug is formed with acylindrical threaded sidewall and a disc like bottom wall. The sidewallterminates in a circumferentially enlarged rim and has an annular gasketseat immediately under the rim. Interposed the plug gasket seat and thesidewall thread is a circumferential gasket retaining lip. A resilientsealing gasket is stretched over the plug gasket seat occupying thevertical space between the plug rim and the retaining lip. The abovedescribed plug is screwed into a container wall opening having aninternal screw thread and an inwardly facing gasket sealing area. Inaccordance with the invention the critical relationship heretoforeexisting between the plug gasket and the container opening thread nowbecomes quite inconsequential. As the plug is backed out of the threadedcontainer opening the gasket is firmly held in place on the plug gasketseat by the novel retaining lip. The resulting clean separation of theplug gasket from the container opening constitutes a significantimprovement over the prior art.

[0008] It is accordingly a principal object of the invention to providean improved threaded closure plug for industrial size containers.

[0009] A further object is to provide a threaded closure plug having anew and improved gasket seat construction.

[0010] A more detailed object is to provide a plug gasket seat withstructure to positively retain the plug gasket thereon during screwingand unscrewing.

[0011] Further and more detailed objects will in part be apparent and inpart pointed out as the description of the invention taken inconjunction with the accompanying drawing proceeds.

[0012] The above and further features of the present invention are setforth in the appended claims and are further described in the drawingswherein:

[0013]FIG. 1 is a part elevational part sectional view of the closureplug in accordance with the invention.

[0014]FIG. 2 is a top plan view of the container closure combination.

[0015]FIG. 3 is part sectional part elevational view of the plug screwedinto the container opening.

[0016]FIG. 4 is a view similar to FIG. 3 but with the plug in partiallyunthreaded position.

[0017]FIG. 5 is a view similar to FIG. 4 illustrating the prior art.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The closure plug of the invention generally indicated at numeral1 has a disc like bottom wall 2 surrounded by a cylindrical sidewall 3terminating in a circumferentially enlarged rim 4. The interior of theplug 1 has a series of wrench engaging lugs 5 for imparting screwing andunscrewing torque to the plug. The plug sidewall 3 has a pilot portion 6extending from the bottom wall 2, an external helical screw thread 7 anda gasket seat 8 positioned immediately below the plug rim 4. Here it isimportant to note that the gasket seat 8 lies in plane axially alignedwith the plug thread root diameter. This relationship is beneficial inassuring a sufficient gasket volume between the plug and the matingcontainer opening surface to close off any leakage path. The plugsidewall 3 is formed with a circumferential retaining lip 9 at the upperend of the thread 7 which extends radially outwardly in axial alignmentwith the thread crest. As clearly seen in FIG. 1 the plug thread runsout and terminates at the point 10 within the lip 9 leaving a uniformupwardly facing annular surface 11 immediately above the threadtermination 10. A resilient annular sealing gasket 12 having asubstantially square cross sectional shape is stretched over the plug soas to hug the gasket seat 8. The gasket thus positioned is snuglyclamped between the undersurface 4 a of the plug rim 4 and the uppersurface 11 of the retaining lip 9 making dislodgement of the gasket 12from the gasket seat 8 quite unlikely.

[0019] The container wall opening within which the plug 1 is threadedlyengaged is clearly shown in FIG. 2 and consists of a container wall 20within which a bushing generally indicated at numeral 21 is inserted ina conventional manner. The bushing 21 has a circumferentially extendingpolygonal base 22, a cylindrical wall 23 extending therefrom andterminating in a radially outwardly curled bead 24. The container wall20 overlies the polygonal base 22 in a mating embossment 25 and has anupstanding substantially cylindrical neck 26 which extends within thebushing curl 24. A bushing gasket 27 is compressed between the bushing21 and the surrounding surfaces of the container wall 20. An internalhelical screw thread 28 is formed on the bushing wall 23 extending fromthe base 22 to a thread run-out point 29 at the start of the bead 24.The upwardly extending unthreaded bead portion immediately above thethread run-out point 29 forms a smooth gasket sealing area 30.

[0020] The sealing relationship between the plug 1 and bushing 21 infully torqued condition as depicted in FIG. 3 shows the plug gasket 12tightly compressed between the plug gasket seat 8 and the bushingsealing area 30. Quite noticeably the gasket 12 is also axiallyrestrained between the rim undersurface 4 a and the upper surface 11 ofthe retaining lip 9. Moreover it can be seen that the gasket 12 in thistightened position lies in contact with the bushing thread helicalrun-out and termination point 29. The continuous annular upper surfaceof the retaining lip maintains a constant axial spacing from the rimunder surface 4 a and prevents the gasket 12 from at any point becomingensnared in the bushing thread 28. Upon unscrewing of the plug as shownin FIG. 4, the retaining lip 9 very clearly lifts the plug gasket 12away from the bushing thread 28 and up off of the gasket sealing area30. It is due to this clean separation of the plug gasket from thesurrounding bushing surfaces that the heretofore common gasket“gripping” and gasket “looping” problems have been eliminated.

[0021] Turning to FIG. 5 which in contrast shows a typical prior artcondition wherein a prior art plug 40 is unscrewed from an internallythreaded container wall opening neck 41. Here the plug gasket 42 sits onthe gasket seat 43 formed at the root diameter of the plug thread butthe plug thread 44 simply diminishes indicated by numeral 45 as itapproaches the gasket seat 43. Under these prior art conditions it canbe seen that as the plug is backed off, the gasket 42 has almost noaxial support supplied by the diminished thread 45. As a result thegasket becomes easily ensnared between the interengaging closure threadsand is pulled off of the gasket seat creating a serious obstruction tonormal closure functionality.

[0022] Various changes in or modifications of the gasket retaining plugof the invention would suggest themselves to those skilled in the artand could be made without departing from the spirit or scope of thisinvention. For example, the invention plug could be either molded fromsynthetic plastic resin or machined from metal. It is accordinglyintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as being illustrative andnot in a limiting sense.

I claim:
 1. A closure plug formed with a cylindrical sidewall having ahelical screw thread, said sidewall terminating in a circumferentiallyenlarged rim, an annular gasket seat immediately under said plug rim insubstantial axial alignment with said screw thread root diameter and acircumferential gasket retaining lip interposed said plug gasket seatand said sidewall thread.
 2. The closure plug as in claim 1, whereinsaid sidewall thread runs out and terminates at a point within saidretaining lip; leaving a uniform upwardly facing annular surfaceimmediately above said thread termination.
 3. An externally threadedclosure plug for tightly sealing off an internally threaded containerwall opening, said plug formed with a cylindrical sidewall, a helicalscrew thread formed on said sidewall, a circumferentially enlarged rimsurrounding one end of said sidewall an annular gasket seat formed insubstantial axial alignment with said screw thread root diameter on saidsidewall interposed said rim and said screw thread and circumferentialgasket retaining means formed on said sidewall interposed said threadand said gasket seat.
 4. A closure plug as in claim 3 including asealing gasket positioned on said gasket seat.
 5. A closure plug as inclaim 4, said sealing gasket being tightly confined within the radiallyopening annular groove formed by said rim and said gasket seat and saidgasket retaining means.
 6. A closure plug as in claim 3 and said gasketretaining means extending radially outwardly from said gasket seat.
 7. Aclosure plug as in claim 6 and said gasket retaining means presenting acontinuous annular surface substantially parallel to said rim.
 8. Incombination an externally threaded closure plug and a container wallopening, said container wall opening having an internally threadedportion and an unthreaded portion, said closure plug having acylindrical sidewall, a screw thread on said sidewall, acircumferentially enlarged rim surrounding said sidewall, an annulargasket seat formed on said sidewall, a gasket compressed between saidunthreaded opening portion and said gasket seat, said gasket lying inclose proximity to said internal thread and gasket retaining means onsaid plug sidewall interposed said plug thread and said gasket seatpreventing interengagement of said gasket and said opening internallythreaded portion whereby unimpeded unscrewing of said plug and gasket asan undisturbed unit is effected.
 9. The combination as in claim 8wherein said container wall unthreaded portion extends upwardly andradially outwardly from said gasket retaining means.
 10. The combinationas in claim 8 and said sealing gasket being tightly confined by said rimand said gasket retaining means.
 11. The combination as in claim 10 andsaid gasket retaining means presenting a continuous annular surfacesubstantially parallel to said lip rim.
 12. The combination as in claim11 and said gasket retaining means extending radially outwardly to apoint spaced from said opening unthreaded portion.